The Myth: Islands Are Less Prone to Biological Invasion

A common misconception is that island ecosystems are less susceptible to biological invasions because their remoteness acts as a natural barrier. The logic behind this idea is straightforward: greater distance from the mainland should reduce the number of invasive species that can reach and establish themselves on islands.

However, this belief does not hold up under scientific scrutiny. In reality, islands are among the ecosystems most severely impacted by biological invasions.

The Reality: Islands Are Exceptionally Vulnerable

Why Are Islands So Vulnerable?

• Low Species Diversity: Islands typically have fewer species and simpler food webs compared to continental ecosystems. This lack of diversity means there are more unoccupied ecological niches for invaders to exploit.

• Lack of Natural Predators and Competitors: Many island species have evolved in isolation, without exposure to strong competitors, predators, or herbivores. As a result, they often lack the defensive adaptations necessary to withstand invasive species.

• High Endemism: Islands harbor a large number of endemic species—organisms found nowhere else on Earth. These unique species are especially at risk of extinction when faced with aggressive invaders.

• Human Activity: Increased global trade, tourism, and transport have made it easier than ever for invasive species to reach even the most remote islands. Once introduced, these species can spread rapidly due to the lack of natural checks and balances.

Scientific studies confirm that biological invasions present a global threat to biodiversity, with oceanic islands being the hardest hit. The severity of invasion often increases with the isolation of the island, not the other way around. This is because isolated islands are even less prepared to cope with new species, and their native biota are poorly adapted to defend against invaders13458.

Characteristics of Invasive Species

Invasive species possess certain traits that make them particularly effective at colonizing new environments:

• Greater Phenotypic Plasticity: Invasive species often exhibit a high degree of phenotypic plasticity, meaning they can adjust their growth, reproduction, and behavior to suit a wide range of environmental conditions. This flexibility gives them a competitive edge over native species.

• High Dispersal Ability: Many invasive species have evolved mechanisms for rapid and widespread dispersal, allowing them to colonize new areas quickly.

• Aggressive Growth and Reproduction: Invasive species often grow faster, reproduce more prolifically, and can outcompete native species for resources.

The Role of Ecosystem Diversity

Another important point is the relationship between ecosystem diversity and invasibility. At large spatial scales, studies have found that diversity-rich ecosystems can actually be more prone to invasion. This is because a greater diversity of habitats and resources can support a wider range of invaders, and more opportunities exist for species to establish themselves.

The Correct Answer Explained

Given the statements:

1. Island ecosystems are less prone to biological invasion because of their distance from mainland

2. Invasive species have greater phenotypic plasticity compared to native species

3. Invasive species have high dispersal ability

4. At a large scale, diversity-rich ecosystems are generally more prone to invasion

Statement (1) is NOT correct.
Scientific evidence shows that island ecosystems are highly vulnerable to biological invasions, regardless of their distance from the mainland. In fact, their isolation often makes them more susceptible, not less13458.

Statements (2), (3), and (4) are correct and supported by ecological research.

The Impact of Invasive Species on Island Ecosystems

The consequences of biological invasions on islands are often severe:

• Loss of Native Species: Invasive predators, herbivores, and competitors can drive native species to extinction.

• Ecosystem Disruption: Invasive species can alter nutrient cycling, fire regimes, and other ecosystem processes.

• Economic and Social Costs: Invasions can impact agriculture, fisheries, tourism, and human health.

Conclusion

Contrary to popular belief, island ecosystems are not protected from biological invasions by their remoteness. Instead, their unique characteristics make them especially vulnerable to the introduction and spread of invasive species. Understanding this reality is crucial for effective conservation and management strategies aimed at protecting island biodiversity.